Definitely a bowfin, but killing them is terrible advice. Bowfin are a native species to many Wisconsin waters and have been around longer than almost any other species there. They, like all other native species, are a crucial component to the eco system on that lake and killing them just to kill them is a pretty ignorant move. Besides, as you discovered, they are an amazing fighting fish that will readily hit lures like any prized game fish. They are a blast on top water.
There is a ton of information out there on the web about bowfin and other native Wisconsin species. Here is an article from the WDNR about some native species of fish with declining numbers and the challenge that poses to the eco system.
http://dnr.wi.gov/wnrmag/html/stories/2 ... /shore.htm
